test(indexing): cross-modality ModalityWorker.derive+sync contract supplement

[earayu]

Summary

Per @earayu2 / @不穷 standby task (msg=981ae30d) — supplement the existing per-modality acceptance tests in test_t1_2_graph.py / test_t1_3_vector_fulltext.py / test_t1_4_summary_vision.py with cross-modality contract tests that exercise invariants the spec promises across all 5 modalities.

Disjoint with PR #1729 (Wave 3 hard-cut) — this branch is based on origin/main and verified passing against the pre-Wave-3 codebase. Per PM msg=ca69198a: open in parallel, no merge dependency on Wave 3.

Coverage (11 tests, +456 LOC, 1 new file)

1. §C.7 reschedule contract (2 tests): summary + vision derive() with a missing upstream source returns DeriveResult(derived_artifact_path="") (the empty-string signal the orchestrator interprets as "derive incomplete, leave PENDING for next reconciler cycle"). Vector + fulltext are pass-through and covered by existing per-modality "no-op on missing chunks" tests.

2. N-call replay convergence (4 tests, parametrized vector/fulltext/summary/vision): 5 consecutive sync() calls produce a backend state byte-equivalent to a single sync — extends existing 2-call tests under arbitrary retry storms (§D.4).

3. Cross-document parse_version isolation (4 tests, parametrized): sync() of doc-A's (doc_a, parse_version) slot must NOT touch doc-B's backend state. Locks the §D.1 DELETE scope: WHERE document_id=A AND parse_version=V only. Uses two distinct doc bodies because the parser's content-hashed chunk_id would otherwise collide cross-doc (fixture limitation, not production-code invariant violation; called out in test docstring).

4. All-5-modality enum discriminator (1 test): each ModalityWorker subclass binds the class-level modality attribute to the matching Modality enum value — orchestrator route key, a misbind would silently mis-route work.

Graph modality is intentionally NOT in the parametric sweeps because test_t1_2_graph.py already covers the §D.3 lineage semantic exhaustively (D3.6 5-step scenario + Nebula race + byte-equivalent re-sync + tenant_scope_key propagation). The all-5-modality enum test is the only graph touch here.

Test plan

• pytest the new file → 11 passed (against origin/main)
• pytest the new file → 11 passed (against chenyexuan/celery-wave3-cutover Wave 3 branch — Wave 3 model NOT NULL flip + dispatcher changes don't perturb ModalityWorker contracts)
• ruff check + format --check clean
• CI lint-and-unit + e2e-http-smoke + e2e-http-provider + provider-preflight (CI to run)

🤖 Generated with Claude Code